Marine propeller



May 28, 1968 P. KAPLAN ETAL 3,385,374

MARINE PROPELLER Filed Jan. 23, 1967 5 sheets-sneek 1 May 28, 1968 P.KAPLAN ETAL 3,385,374

MARINE PROPELLER Filed Jan. 2s, 1967 s sheets-sheet a ff fame ThrustFarce Flc-5.2

Bray Farce FIG.3B

lNvENToRs- Paz/Z Kapla BY Huff/.sf Zeman Hyg/yay Afro/wins May 28, 1968P, KAPLAN ETAL MARINE PROPELLER 3 Sheets-Sheet 5 Filed Jan. 23, 1967FIG.6

INVENTORS United States Patent O 3,385,374 MARINE PROPELLER Paul Kaplan,Jericho, and August F. Lehman, Centerport, N.Y., assignors to Oceanics,Inc., Plainview, N.Y., a corporation of Delaware Filed Jan. 23, 1967,Ser. No. 616,999 4 Claims. (Cl. 170-135.4)

ABSTRACT OF THE DISCLOSURE A marine screw propeller having internalducting connected to a huid-pressure source by means of which lluid isdischarged as a jet sheet at a predetermined velocity and angle fromcritical locations on the blade surface in the area of the trailingedge. The parameters of the blade and jet are so arranged that acondition of super-circulation is induced resulting in a lift forcewhich exceeds the theoretical maximum obtainable due to camber and angleof attack.

Many attempts have been made to improve the efciency of propellers,particularly when the propeller develops high thrust. Due to theoccurrence of cavitation or the separation of the water from the blades,or a cornbination of both, there is a limitation on the thrust andetliciency which can be normally obtained under any given operatingconditions. For any given propeller geometry, rotational speed, inflowvelocity and depth of submergence, there is, in addition to apredetermined relation between thrust and eliciency, a maximum thrustbeyond which the propeller can not be operated without the occurrence ofthe adverse eiects of separation and/ or cavitation.

It is an object of the present invention to provide an improved marinescrew propeller and propeller system, capable of operating with higherthrust and eiliciency than are attainable under present techniques anddesigns.

It is another object of the invention to provide a method for achievingsuper-circulation conditions in a marine screw propeller.

Still another object of the invention is to provide a marine screwpropeller design which can be made structurally strong without making itsusceptible to cavitation and decreased eiciency.

In accordance with the present invention, increased thrust and eiciencyare obtained from marine screw propellers through the control of thepressure distribution on the blades by inducing a condition ofsuper-circulation, which is defined as a means of developing a liftforce which exceeds the theoretical maximum attainable with any givenpropeller blade geometry by virtue of changes in camber and angle ofattack. By discharging a jet of predetermined size and velocity, and ata predetermined angle from critical locations on the blade,super-circulation is attained which enables the blade to operate at highciciency and thrust.

In accordance with one embodiment of the invention, the propeller isdriven by a combination of torque applied to the propeller shaft and bythe torque developed by the jet momentum reaction which occurs as aresult of the discharge of jets from the trailing edges of the blades.Propellers driven by drive shaft torque 'or jet momentum reactiongenerated by fluid discharge from the blades, as well as a combinationof the two, are known in the art. In all cases, however, the total liftforce which can be generated by the blades is limited by the phenomenaof cavitation and/or separation of the liquid operating medium from thesurfaces ot' the blades. The present invention utilizes a jet dischargein the form of a jet ap in the vicinity of the trailing edges of theblades which is critically shaped in width, length, angle of discharge,and veice locity, to induce super-circulation, in addition to thebenefit which results incidentally from the jet momentum recovery of thejet. There results augmented thrust without the danger 0f a decrease ofeliciency resulting from cavitation or separation associated with highblade loadings. This is achieved with the jet ilap by modifying thechordwise pressure distribution of the foil so as to reduce the pressurepeaks occurring with normal distributions while increasing the overallload developed by the pressure distribution profile.

Preferred embodiments of the invention, as well as other features andadvantages thereof, will be understood from the following specificationtaken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a view of one of the blades and a portion of the hub of amarine screw propeller in plan view, i.e., looking in the direction ofthe drive shaft of the propeller;

FIGURE 2A is a chord section view in enlarged scale of the blade, takenon the line 2 2 of FIGURE 1 looking in the direction of the arrows,showing the lift and thrust force vectors of both the foil eiiect andthe jet-induced super-circulation effect, the latter vector including arelatively small jet momentum reaction component;

FIGURE 2B is a partial chord section similar to FIG- URE ZA but inlarger scale to illustrate the jet slot width limits;

FIGURE 2C is a chord section view corresponding to FIGURE 2A showing thelift and thrust yforce vectors of a propeller in which there is a jetdischarge aligned with the nose-tail line of the blade section so thatsuper circulation does not occur although the jet momentum reactiontorce remains;

FIGURE 3A is a diagrammatic view of a chord section of a blade or foilshowing, superimposed thereon, a plot of the pressure distribution whichoccurs when the blade is driven at incidence without the presentinvention;

FIGURE 3B is a view of the blade of FIGURE 3A, showing a plot of theupper surface pressure distribution utilizing a jet ilap deflection inaccordance with the present invention;

FIGURE 4 is a View in longitudinal section of the stern of a ship takenthrough the axis of the drive shaft and including a propeller and driveshaft assembly embodying the present invention;

FIGURE 5 is a view in horizontal section through the stern of the shipof FIGURE 4, illustrating one representative mechanism for introducingfluid under pressure into the propeller blades; and

FIGURE 6 is a plan or full-face view, looking the direction ofthe axisofthe drive shaft of the propeller of FIG- URE 4 and having one of isfour blades illustrating internal ducting by a section passing throughall of the chord lines of the blade.

Referring to the drawings, the invention is illustrated as embodied in amarine screw propeller 10 (FIGURES 4 and 6) attached to a hollow tail ordrive shaft section 11 in a ship 12 (illustrated only diagrammaticallyto show the underwater portion of the stern). One of the blades 19a ofthe propeller lil is illustrated in enlarged scale in FIGURE 1 and instill larger scale in FIGURES 2A and 2B.

IEach of the four blades, 10a' b, c and a' of the propeller 10 includesinternal ducting of the type indicated generally by the numeral 13 inthe blade section 19a. For purposes of tlow control, the ducting 13 ispreferably divided into discrete ducts 13a, b and c by means ofcontoured inner partitions 14a and b, terminating at the trailing edge1S of the blade in an elongated discharge opening or series of openings16, best seen in FIGURES 1 and 6, adapted to discharge a iluid jet sheetI (FIGURE 4) from the surface of the blade opposite the suction or lowpressure side of the blade. The inner hub openings and the iluidpassageways are so designed so as to control the exit velocity of theuid at the trailing edge. It will be observed that the slot 16 extendsover a substantial length of the trailing edge of the blade from a pointnear the central hub 17 to a point near the blad-e tip to approximatelythe 0.85 radius of the blade.

The drive shaft section 11 to which the propeller 10 is affixed ishollow and includes, in its portion disposed within the propeller,radial ports or openings I8 which place the interior conduit Ila of theshaft 11 in communication with the ducts 13a, b and c of each of theblades. In accordance with the invention, the jet velocity at any givenpoint along lthe length of the jet ap discharge J should exceed themagnitude of the local water velocity at the particular point. Thus thesizes of the ports `1'8 as lwell as the sizes of the ducts t13a, b and ccan be selected and arranged to achieve this result. The low path fromthe interior of the shaft l1 into each of the blades is furthercontrolled by a tapered plug 18a.

The drive shaft il, between the main propulsion motor (not shown) of theship and the propeller, passes through a stationary collector box 19having seals 19a and 1913. The collector is connected by suitableconduits 20 and 21 to the output sides of pumps 22 and 23, the pumpshaving their input sides connected by conduits 24 and 25 to suitableopenings in the ships hull beneath the water line, preferably at pointshaving high pressures. The hollow drive shaft section 11, within thecollector box 19, is formed with radial openings 26 communicating withthe hollow interior. A contoured plug 27 can be included within thehollow shaft within the collector 19 to promote uniform flow.

In operation, torque is applied to the drive shaft in the conventionalmanner by means of the main propulsion engine and, in addition, uid ispumped through the ducts 113 and out of the slots 16 in a jet flap. Thepumps 22 and 23 are used to supply and to adjust 4the ow rate of thejets to the optimum value, recognizing that some pumping action willoccur automatically, as the propeller rotates, due to the centrifugalforce generated by the turning propeller.

The function of the jet flap emitted from the slots is so arranged inits shape, positioning and flow rate, in accordance with the presentinvention, that super-circulation is induced. The concept of circulationis the basis of airfoil and propeller blade theory. Assuming a finitespan foil, the lift per unit length of span varies directly withcirculation. Lift is expressed as follows:

wherein L equals lift, p equals mass density of the fluid, V equalsfluid velocity, and I equals circulation. Normally the total lift forcewhich can be obtained is limited by the adverse effects of cavitationand separation which occur when certain pressure distributions over thefoil exist. Super-circulation is a term used to describe the creation ofa large lift force by increasing the pressure distribution magnitudeover the foil surface through an increase in I over and above the Iwhich can normally be induced. In the case of the jet ilap produced inaccordance with the present invention, there is a significantaugmentation of the total resulting lift relative to the lift increaseresulting from the jet momentum force alone.

Referring to FIGURES 3A and 3B, it will be seen that the pressuredistribution on a foil due to super-circulation induced by the jet iiap(FIGURE 3B) differs considerably from that created by the foil atincidence (FIGURE 3A). In the case of the pressure distributionsresulting from the jet ilap, it will be seen that a total lift forcefrom the pressure distribution is achieved without the pressure peakassociated with the generation of the same total lift through foilincidence. The limit of the maximum thrust obtained with incidence,camber, or both, is exceeded significantly by -the jet flap inducedsuper-circulation effect. Also, the reduction in the maximum pressurepeak magnitude for the case of the jet flap pressure pattern acts toinhibit the possibility of separation as well as the susceptibility tocavitation.

Referring now to FIGURE 2A, the jet ilap is discharged at an angle 1- tothe nose tail line of the blade 10a. The angle 1- is illustrated asbeing approximately 30 degrees, although as described below it can varyover a range of angles. It should be noted that there is a component ofthe jet momentum which reacts in the direction of rotation of the bladeand a component which acts in the direction of travel of the vehicle.The latter component less the drag loss constitutes a net thrust gain ofrelatively small magnitude and is insignificant for practical andachievable ilow rates that would yield etiicient operation. U.S. PatentNo. 2,511,156, discloses a marine screw propeller in which this reactioncomponent is utilized to augment the thrust of the propeller. Thecomponent in the direction of rotation of the propeller is alsoinsignificant for practical and achievable ow rates. This force has alsobeen used in the prior art as a means of driving the propellers and isdescribed in U.S. Patent No. 2,705,- O51. These two effects whichnecessarily result in the practice of the present invention are, asstated, relatively insignicant when reduced 4to practice.

The lift force to which the present invention is directed is thatindicated by the vector bearing the legend Additional Lift Due toSuper-Circulation. To achieve supercirculation:

(a) the width of the jet ap or stream,

(b) the angle of the jet flap or stream,

(c) the velocity of the jet Hap or stream, and

(d) the radial location on the blade of the jet flap or stream,

are interrelated and must be coordinated. In accordance with theinvention, the thickness of the jet sheet, i.e. the slot width, must bebetween approximately 0.005 and 0.03 of the blade chord as shown inFIGURE 2B; the jet stream angle must be between approximately 15 and 75degrecs from the nose tail line of the blade prole at each particularradial section of the propeller as shown in FIGURE 2A; the velocity ofthe jet stream must be greater than the resultant water velocity at eachparti-cular radial section of the propeller; and the majority of the jetstream must be emitted between the blade root and approximately the 0.85radial section as shown in FIGURE 1, with the jet slot being located inthe region of the trailing edge of the blade or inward up to a distanceof 0.15 chord as also shown in FIGURE 2A. While any combination of theabove parameters will induce some degree of super-circulation about theblade, it will be understood that for a particular propeller design theparameters can be optimized to achieve a loading per unit area of theblade which can be increased tive to ten times over conventional averagedesign loadings (loadings obtainable without the jet ap action) withoutincreasing cavitation susceptibility. The driving torque of thepropeller is supplied by the main drive shaft and the increase in thrustloading is achieved without a corresponding increase in shaft torque.Thus, the eiciency of the propeller is increased for any given requiredamount of total thrust.

While the invention has been described above having reference topreferred embodiments thereof, it will be understood that it can takevarious other forms and arrangements within the scope of the invention.Thus, for example, the means for supplying fluid to the ducts within theblade can be widely varied, as can the geometry of the blades and theinternal ducting. Also, while the jet fluid used in the embodiment ofthe invention described herein is water, other liquids can be used ascan gasses such as steam, air, machinery exhaust gas and the like. Theinvention should not, therefore, be regarded as limited except asdefined by the following claims.

We claim:

1. A marine screw propeller comprising a hub portion and a plurality ofblades extending radially therefrom, each having a curvilinear foilsurface, fluid duct means in the blades, and uid discharge openingsdisposed adja- -cent the trailing edges of the blades and disposedprimarily in the space between the blade root and the'0.85 radialsection of the blade to discharge fluid from said duct means in a shapedjet stream, said iluid duct means having inlet means communicating withsaid hub portion, said openings being shaped and arranged to direct thejet stream at an angle of between approximately 15 and 75 degrees to thenose-tail line of each radial profile of the blades and in a directionhaving a component opposite to the direction of thrust of the blades,and means to pass iluid through said duct means from the openings at avelocity greater than the resultant water velocity at each radialsection of the blade, and having a predetermined magnitude to achievepredetermined local loading thereon and to establish super-circulationabout the blades.

2. Apparatus as set forth in claim 1, the width of the openings beingbetween approximately 0.005 and 0.03 of the blade chord.

3. Apparatus as set forth in claim 1, said duct means in each bladecomprising a plurality of generally coplanar ducts separated by internalpartitions, and ports in the hub communicating with the ducts, with thesaid duct and port dimensions and contours controlling the uid dischargevelocity along the length of shaped jet discharge.

4. Apparatus as set forth in claim 1 said discharge openings beingdisposed on the side of the blade Opposite the suction surface and inthe space within a distance of approximately 0.15 chord length from thetrailing edge.

References Cited UNITED STATES PATENTS 736,952 8/1903 Fox 170-1721,119,178 12/1914 Krantz 170--172 X 1,190,755 7/1916 Hahn 170--1722,169,325 8/1939 Novak 170-172 X 3,109,495 11/1963 Lang.

3,209,714 10/1965 Bowles.

FOREIGN PATENTS 505,082 8/1954 Canada.

774,396 5/ 1957 Great Britain.

124,583 4/ 1949 Sweden.

EVERETTE A. POWELL, I R., Primary Examiner.

